Method for producing titanium-doped synthetic quartz glass

Patent metadata

Field	Value
Publication number	US-9796617-B2
Application number	US-201414767466-A
Country	US
Kind code	B2
Filing date	Feb 7, 2014
Priority date	Feb 12, 2013
Publication date	Oct 24, 2017
Grant date	Oct 24, 2017

Abstract

A method for producing titanium-doped synthetic quartz glass includes:
(A) providing a liquid SiO 2 feedstock material that comprises more than 60% by weight of the polyalkylsiloxane D4; (B) evaporating the liquid SiO 2 feedstock material to produce a gaseous SiO 2 feedstock vapor; (C) evaporating a liquid TiO2 feedstock material to produce a gaseous TiO2 feedstock vapor; (D) converting the SiO 2 feedstock vapor and the TiO2 feedstock vapor into SiO2 particles and TiO2 particles, respectively; (E) depositing the SiO2 particles and the TiO2 particles on a deposition surface while forming a titanium-doped SiO 2 soot body; (F) vitrifying the titanium-doped SiO 2 soot body while forming the synthetic quartz glass, whereby the TiO2 concentration of the synthetic quartz glass is between 5% by weight and 11% by weight.

The liquid SiO 2 feedstock material comprises at least one additional component made of the polyalkylsiloxane D3 having a weight fraction of mD3 and one additional component made of the polyalkylsiloxane D5 having a weight fraction of mD5 at a weight ratio of mD3/mD5 in a range of 0.01 to 1, and the liquid SiO 2 feedstock material provided is evaporated while maintaining the weight ratio of mD3/mD5 and at least 99% by weight thereof are evaporated to form the gaseous SiO 2 feedstock vapor.

First claim

The invention claimed is:

1. A method for producing titanium-doped synthetic quartz glass comprising:
(A) providing a liquid SiO 2 feedstock material comprising more than 60% by weight of the polyalkylsiloxane D4;
(B) evaporating the liquid SiO 2 feedstock material to produce a gaseous SiO 2 feedstock vapor;
(C) evaporating a liquid TiO2 feedstock material to produce a gaseous TiO2 feedstock vapor;
(D) converting the SiO 2 feedstock vapor and the TiO2 feedstock vapor into SiO2 particles and TiO2 particles, respectively;
(E) depositing the SiO2 particles and the TiO2 particles on a deposition surface while forming a titanium-doped SiO 2 soot body;
(F) vitrifying the titanium-doped SiO 2 soot body while forming the synthetic quartz glass, whereby the TiO2 concentration of the synthetic quartz glass is between 5% by weight and 11% by weight;
wherein the liquid SiO 2 feedstock material comprises at least one additional component made of the polyalkylsiloxane D3 having a weight fraction of mD3 and one additional component made of the polyalkylsiloxane D5 having a weight fraction of mD5 at a weight ratio of mD3/mD5 in a range of 0.01 to 1, and the liquid SiO 2 feedstock material provided is evaporated while maintaining the weight ratio of mD3/mD5 and at least 99% by weight thereof are evaporated to form the gaseous SiO 2 feedstock vapor.

2. The method according to claim 1 , wherein the evaporation comprises:
heating the TiO2 feedstock material; and
introducing the heated TiO2 feedstock material into an expansion chamber such that at least a first portion of the TiO2 feedstock material evaporates as a result of a drop in pressure.

3. The method according to claim 1 , wherein the evaporation comprises:
heating the TiO2 feedstock material;
introducing the heated TiO2 feedstock material into an expansion chamber; and
mixing the TiO2 feedstock material with a heated diluting agent such that at least a second portion of the TiO2 feedstock material evaporates as a result of a lowering of the dew point.

4. The method according to claim 2 , wherein at least 99.95% by weight of the TiO2 feedstock material is transitioned into the TiO 2 feedstock vapor as a result of the drop in pressure and/or lowering of the partial pressure.

5. The method according to claim 1 , wherein the TiO2 concentration of the synthetic quartz glass is between 7% by weight and 10% by weight.

6. The method according to claim 5 , wherein the TiO2 concentration of the synthetic quartz glass is between 7.8% by weight and 8.9% by weight.

7. The method according to claim 1 , wherein the Ti3+ concentration of the synthetic quartz glass is between 1 ppm and 200 ppm.

8. The method according to claim 7 , wherein the Ti3+ concentration of the synthetic quartz glass is between 1 ppm and 20 ppm.

9. The method according to claim 1 , wherein a variation □Ti3+/Ti3+ of the Ti3+ concentration of the synthetic quartz glass at a surface used for optical purposes is 0.8 or less.

10. The method according to claim 9 , wherein a variation □Ti3+/Ti3+ of the Ti3+ concentration of the synthetic quartz glass at a surface used for optical purposes is between 0.0002 and 0.5.

11. The method according to claim 1 , wherein the internal transmission at a path length of 1 mm in a wavelength range from 400 nm to 700 nm is at least 80%.

12. The method according to claim 11 , wherein the internal transmission at a path length of 1 mm in a wavelength range from 400 nm to 700 nm is at least 90%.

13. The method according to claim 1 , wherein a fictive temperature of the synthetic quartz glass is maximally 1,050° C.

14. The method according to claim 13 , wherein a fictive temperature of the synthetic quartz glass is maximally 950° C.

15. The method according to claim 1 , wherein the thermal expansion coefficient in a temperature window from 0° C. to 100° C. is maximally 0±150 ppb/° C.

16. The method according to claim 1 , wherein the titanium-doped SiO 2 soot body is doped with fluorine.

17. The method according to claim 16 , wherein the fluorine concentration of the synthetic quartz glass is at least 100 ppm by weight.

18. The method according to claim 1 , wherein the polyalkylsiloxane D3, which has a weight fraction of mD3, and the liquid TiO2 feedstock material, which has a weight fraction of mTiO2, are evaporated at a weight ratio of mTiO2/mD3 in a range of 0.1 to 10.

19. The method according to claim 1 , wherein the liquid TiO2 feedstock material comprises at least 80% by weight titanium isopropoxide (Ti{OCH(CH3)2}4).

20. A method comprising:
producing a synthetic quartz glass according to claim 1 ; and
producing EUV mirror substrates from the synthetic quartz glass.

Assignees

• Heraeus Quarzglas

Inventors

• Fabian Heinz
• Thomas Stephan

Classifications

• C03B2207/32

  Non-halide · CPC title

• C03B19/1415 Primary

  Reactant delivery systems · CPC title

• C03C3/06

  with more than 90% silica by weight, e.g. quartz {(C03C3/045 takes precedence)} · CPC title

• C03B2207/34

  Liquid, e.g. mist or aerosol · CPC title

• C03B19/14

  by gas- {or vapour-} phase reaction processes · CPC title